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Articles by M Gaestel
Total Records ( 4 ) for M Gaestel
  C Johansen , C Vestergaard , K Kragballe , G Kollias , M Gaestel and L. Iversen

The association between inflammation and tumorigenesis is well recognized. Mitogen-activated protein kinase-activated protein kinase-2 (MK2) is known to play a pivotal role in inflammatory processes. Here, we studied the effect of MK2-deficiency and tumor necrosis factor (TNF)--deficiency on skin tumor development in mice using the two-stage chemical carcinogenesis model. We found that MK2–/– mice developed significantly fewer skin tumors compared with both TNF-–/– and wild-type mice when induced by initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). The TPA-induced inflammatory response was reduced in both, TNF-–/– mice and MK2–/– mice, but most pronounced in TNF-–/– mice, indicating that a reduced inflammatory response was not the only explanation for the inhibited tumorigenesis seen in MK2–/– mice. Interestingly, increased numbers of apoptotic cells were detected in the epidermis of MK2–/– mice compared with TNF-–/– and wild-type mice, suggesting an additional role of MK2 in the regulation of apoptosis. This was further supported by: (i) increased levels of the tumor suppressor protein p53 in MK2–/– mice after DMBA/TPA treatment compared with controls, (ii) reduced phosphorylation (activation) of the negative p53 regulator, murine double minute 2 in MK2/ mouse keratinocytes in vitro and (iii) a significant decrease in the DMBA/TPA induced apoptosis in cultured MK2–/– keratinocytes transfected with p53 small interfering RNA. Taken together, these findings demonstrate a dual role of MK2 in the early stages of tumor promotion through regulation of both the inflammatory response and apoptosis of DNA-damaged cells. These results also identify MK2 as a putative target for future skin carcinoma therapy.

  T Liu , O. E Guevara , R. R Warburton , N. S Hill , M Gaestel and U. S. Kayyali

Hypoxia triggers responses in endothelial cells that play roles in many conditions including high-altitude pulmonary edema and tumor angiogenesis. Signaling pathways activated by hypoxia modify cytoskeletal and contractile proteins and alter the biomechanical properties of endothelial cells. Intermediate filaments are major components of the cytoskeleton whose contribution to endothelial physiology is not well understood. We have previously shown that hypoxia-activated signaling in endothelial cells alters their contractility and adhesiveness. We have also linked p38-MAP kinase signaling pathway leading to HSP27 phosphorylation and increased actin stress fiber formation to endothelial barrier augmentation. We now show that vimentin, a major intermediate filament protein in endothelial cells, is regulated by hypoxia. Our results indicate that exposure of endothelial cells to hypoxia causes vimentin filament networks to initially redistribute perinuclearly. However, by 1 hour hypoxia these networks reform and appear more continuous across cells than under normoxia. Hypoxia also causes transient changes in vimentin phosphorylation, and activation of PAK1, a kinase that regulates vimentin filament assembly. In addition, exposure to 1 hour hypoxia increases the ratio of insoluble/soluble vimentin. Overexpression of phosphomimicking mutant HSP27 (pmHSP27) causes changes in vimentin distribution that are similar to those observed in hypoxic cells. Knocking-down HSP27 destroys the vimentin filamentous network, and disrupting vimentin filaments with acrylamide increases endothelial permeability. Both hypoxia- and pmHSP27 overexpression-induced changes are reversed by inhibition of phosphatase activity. In conclusion hypoxia causes redistribution of vimentin to a more insoluble and extensive filamentous network that could play a role in endothelial barrier stabilization. Vimentin redistribution appears to be mediated through altering the phosphorylation of the protein and its interaction with HSP27.

  J Zhu , X Wu , S Goel , N. M Gowda , S Kumar , G Krishnegowda , G Mishra , R Weinberg , G Li , M Gaestel , T Muta and D. C. Gowda

Proinflammatory responses induced by Plasmodium falciparum glycosylphosphatidylinositols (GPIs) are thought to be involved in malaria pathogenesis. In this study, we investigated the role of MAPK-activated protein kinase 2 (MK2) in the regulation of tumor necrosis factor- (TNF-) and interleukin (IL)-12, two of the major inflammatory cytokines produced by macrophages stimulated with GPIs. We show that MK2 differentially regulates the GPI-induced production of TNF- and IL-12. Although TNF- production was markedly decreased, IL-12 expression was increased by 2–3-fold in GPI-stimulated MK2–/– macrophages compared with wild type (WT) cells. MK2–/– macrophages produced markedly decreased levels of TNF- than WT macrophages mainly because of lower mRNA stability and translation. In the case of IL-12, mRNA was substantially higher in MK2–/– macrophages than WT. This enhanced production is due to increased NF-B binding to the gene promoter, a markedly lower level expression of the transcriptional repressor factor c-Maf, and a decreased binding of GAP-12 to the gene promoter in MK2–/– macrophages. Thus, our data demonstrate for the first time the role of MK2 in the transcriptional regulation of IL-12. Using the protein kinase inhibitors SB203580 and U0126, we also show that the ERK and p38 pathways regulate TNF- and IL-12 production, and that both inhibitors can reduce phosphorylation of MK2 in response to GPIs and other toll-like receptor ligands. These results may have important implications for developing therapeutics for malaria and other infectious diseases.

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